Implantable intraluminal device and method of using same in treating aneurysms

ABSTRACT

A method and apparatus for reducing blood flow to an aneurysm proximate to a bifurcation having a source blood vessel a first branch vessel and a second branch vessel, the method comprising: providing a first mesh-like tube of bio-compatible material, the first mesh-like tube exhibiting a porosity index pre-selected to skew blood flow about the bifurcation away from the aneurysm; inserting the first mesh-like tube into the source blood vessel and the first branch vessel; and securing the first mesh-like tube to at least one of the source blood vessel and the first branch vessel, whereby blood flowing from the source blood vessel flows without undue impedance to the first branch vessel and the second branch vessel while being skewed away from the aneurysm.

RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.11/907,675, filed on Oct. 16, 2007, which is a Divisional of U.S. patentapplication Ser. No. 10/910,621, filed on Aug. 4, 2004, now U.S. Pat.No. 7,306,624, which is a Continuation-In-Part (CIP) of U.S. patentapplication Ser. No. 10/216,356, filed on Aug. 12, 2002, now abandoned,which a) claims the benefit of U.S. Provisional Patent Application No.60/332,013, filed on Nov. 23, 2001, and b) is also aContinuation-In-Part (CIP) of PCT Patent Application No. PCT/IL01/00624,filed on Jul. 9, 2001. The contents of all of the above Applications areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to intraluminal devices implantable in ablood vessel for the treatment of aneurysms especially basal apexaneurysms. The invention also relates to methods of treating aneurysmsusing such intraluminal devices.

BACKGROUND OF THE INVENTION

A number of publications as listed at the end of this specification areincorporated herein by reference in their entireties for backgroundinformation and are numerically referenced in the following text.

Intracranial aneurysms are the main cause of nontraumatic subarachnoidhemorrhage and are responsible for about 25% of all deaths relating tocerebrovascular events. Autopsy studies show that the overall frequencyof intracranial aneurysms in the general population is approximately 5percent and suggest that 10 to 15 million persons in the United Stateshave or will have intracranial aneurysms [1]. In approximately 15,000cases (6 cases per 100,000 persons per year), intracranial aneurysmsrupture every year in North America [2]. Rupture of intracranialaneurysms leads to subarachnoid aneurysmal hemorrhage (SAH) which has a30-day mortality rate of 45%, and results in approximately half thesurvivors sustaining irreversible brain damage [1, 2].

The primary goal of treatments for intracranial aneurysm is preventionof the rupture of the aneurysms, thereby preventing bleeding orrebleeding. At the present time, three general methods of treatmentexist. These can be grouped according to their approach: extravascular,endovascular, and extra-endovascular.

The extravascular approach involves surgery or microsurgery of theaneurysm. One surgical procedure is to apply a metallic clip or asuture-ligation across the artery feeding the aneurysm (neck), therebyallowing the aneurysm to clot off and hopefully shrink. Another surgicalprocedure is to “surgically reconstruct” the aneurysmal portion of theartery, by surgically cut out the aneurysm and repairing the vessel byusing a natural or synthetic vessel graft. Both of these surgicalprocedures typically require general anesthesia, craniotomy, brainretraction, and dissection of the arachnoid around the neck of theaneurysm.

Surgical treatment of vascular intracranial aneurysm is accompanied by amortality rate of 3.8% and a morbidity rate of 10.9% [3]. Because of thehigh mortality and morbidity rates, and because the condition of manypatients does not permit them to undergo an open operation, the surgicalprocedure is often delayed or not practical. For this reason the priorart has sought alternative means of treatment.

The development of microcatheters made possible the use of endovascular(catheter-based) procedures. The major advantage of the endovascularprocedures is that they do not require the use of open surgery. They aregenerally more beneficial and have much lower mortality and morbidityrates than the extravascular procedures.

Many variations of endovascular procedures exist of which some of themore important are the following:

1. Placement of embolic material, such as metallic microcoils orspherical beads, inside the aneurysm sac in order to form a mass withinthis sac which will slow the blood flow and generally encourage theaneurysm to clot off and to shrink. To accomplish this procedure, amicrocatheter is guided through the cerebral arteries until the site ofthe aneurysm is reached. The distal tip of the microcatheter is thenplaced within the sac of the aneurysm, and the embolic material isinjected into the sac of the aneurysm. Typical microcatheters suitablefor this procedure are disclosed in U.S. Pat. Nos. 5,853,418; 6,066,133;6,165,198 and 6,168,592.

Widespread, long-term experience with this technique has shown severalrisks and limitations. The method has 4% morbidity and 1% mortality rateand achieves complete aneurysm occlusion in only 52% to 78% of the casesin which it is employed. The relatively low success rate is due totechnical limitations (e.g., coil flexibility, shape, and dimensions)which prevent tight packing of the sac of the aneurysm, especiallyaneurysms with wide necks [3]. Other difficulties are associated withthe presence of preexisting thrombus within the aneurysm cavity, whichmay be sheared off into the parent trunk leading to parent arteryocclusion. Also aneurysm perforation may occur during placement of coilsinto the aneurysm. Additionally, occurrence of coil movement andcompaction may foster aneurysm revascularization or growth.

2. Another endovascular technique for treating aneurysms involvesinserting a detachable balloon into the sac of the aneurysm using amicrocatheter. The detachable balloon is then inflated using embolicmaterial, such as a liquid polymer material or microcoils. The balloonis then detached from the microcatheter and left within the sac of theaneurysm in an attempt to fill the sac and to form a thrombotic massinside the aneurysm.

One of the disadvantages of this method is that detachable balloons,when inflated, typically do not conform to the interior configuration ofthe aneurysm sac. Instead, the aneurysm sac is forced to conform to theexterior surface of the detachable balloon. Thus, there is an increasedrisk that the detachable balloon will rupture the sac of the aneurysm.

3. Stent technology has been applied to the intracranial vasculature.The use of this technology has been limited until recently by the lackof available stents and stent delivery systems capable of safe andeffective navigation through the intercranial vessels. The use of suchstents is particularly difficult with respect to aneurysms in head bloodvessels because of the number of perforating vessels in such bloodvessels, and thereby the increased danger that one or more perforatingvessels may be in the vicinity of such an aneurysm. The same is truewith respect to bifurcations of a blood vessel splitting into one ormore branch vessels, which may also be in the vicinity of an aneurysm.Where the blood supply to an aneurysm is to be reduced, it is criticalthat the blood supply to such perforating vessel or branch vessels, inthe vicinity of the aneurysm not be unduly reduced to the degree causingdamage to the tissues supplied with blood by such perforating or branchvessels.

Thus, there is a serious danger that the placement of a conventionalendovascular stent within the parent artery across the aneurysm neck toreduce blood flow to the aneurysm, to promote intra-aneurysm stasis andthrombosis [4,5].

Stents having portions of different permeabilities are disclosed, forexample, in McCrory U.S. Pat. No. 5,951,599, Brown et al U.S. Pat. No.6,093,199, Wallsten U.S. Pat. No. 4,954,126, and Dubrul U.S. Pat. No.6,258,115.

The McCrory patent discloses a braided stent having a first portion witha relatively high porosity index so as to be highly permeable to bloodflow, and a second portion of lower porosity index so as to be lesspermeable to blood flow. When the stent is deployed, the portion of lowpermeability is located to overlie the neck of the aneurysm, and theportion of high permeability is spaced from the neck of the aneurysm. Abraided stent construction with different porosities is also disclosedin the Dubrul patent.

Brown et al, on the other hand, discloses an intraluminal device orstent comprising a diverter, in the form of a low-permeability foam pad,to overlie the neck of the aneurysm, straddled on its opposite sides bya pair of high-permeability coil elements for anchoring the device inthe blood vessel.

Wallsten U.S. Pat. No. 4,954,126, discloses a braided tube intraluminaldevice for use in various applications, one of which applications is toapply a graft to treat an aneurysm (FIG. 9). In this case, the completebraided tube would have high permeability with respect to blood flowtherethrough since its function is to mount the grafts, but the graftwould have low-permeability to decrease the possibility of rupture ofthe aneurysm.

Delivery devices for stents for use in the intracranial vasculature arewell known at the art. Typical devices are disclosed, for example, inthe following U.S. Pat. Nos. 5,496,275; 5,676,659; and 6,254,628. Theblood vessels in the brain are frequently as small as severalmillimeters, requiring that the catheters have an outside diameter assmall as 2-8 French (0.66 mm to 2.64 mm).

Technically it is very difficult to produce and accurately deploy thestents described in the above McCrory, Brown et al and Wallsten patentsfor treating aneurysms by using presently available delivery systems.The difficulties include not only in producing such stents of differentpermeabilities, but also in deploying them such that the portion of lowpermeability is exactly aligned with the aneurysm neck. When the deviceis to be implanted in a blood vessel having an aneurysm at or proximateto a perforating vessel or a bifurcation leading to a branch vessel, theportion of high permeability must be precisely located at theperforating or branch vessels in order to maintain patency in theperforating or branch vessels. Additionally, particularly in tortuous,ectatic vessels, existing stiff stents are difficult to introduce andmay results in kinking such as to cause the failure of the deploymentprocess.

Furthermore, none of the prior art mentioned is suitable for use with abasal apex aneurysm.

For these reasons it is apparent that there is a need for a betterintraluminal device to treat an aneurysm, particularly an intracranialaneurysm, and more particularly an intracranial aneurysm proximate to abifurcation.

OBJECTS AND BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide an intraluminal devicehaving advantages in one or more of the above respects for implantationin a blood vessel having an aneurysm in order to treat the aneurysm.Another object of the invention is to provide such an intraluminaldevice particularly useful for implantation in a blood vessel having ananeurysms at or proximate to a bifurcation leading to a branch vesselsuch as to skew the blood flow away from the aneurysm while stillmaintaining patency in the perforating and/or branch vessels.

Another object of the invention is to provide an implantableintraluminal device for treating aneurysms in the intracranialvasculature that is sufficiently flexible and pliable so that it can bedelivered easily to an intracranial site, deployed accurately, and thenleft in position to accomplish its purpose.

A further object of the invention is to provide a method of treatinganeurysms by using intraluminal devices having the above features.

The present invention provides an intraluminal device implantable in thevicinity of a blood vessel bifurcation, the bifurcation having a sourceblood vessel a first branch vessel and a second branch vessel, ananeurysm being located proximate to the bifurcation, the devicecomprising: a mesh-like tube of bio-compatible material having anexpanded condition in which the tube diameter is larger than thediameter of the blood vessel in which it is to be implanted, themesh-like tube having a length sufficient to be anchored to both thesource blood vessel and the first branch vessel thereby straddling theopening of the second branch vessel; the mesh-like tube also having alength such that, when placed and anchored to straddle the opening ofthe second branch vessel, it also straddles said aneurysm; the mesh-liketube being dimensioned and configured to have in its implanted conditiona porosity index such as to skew the flow of blood away from theaneurysm sufficiently to decrease the possibility of rupture of theaneurysm but not to unduly reduce the blood flow to the second branchvessel to a degree likely to cause significant damage to tissuessupplied with blood by such second branch vessel. The foregoingadvantageous results have been found attainable when the mesh-like tubeis designed to have, in its expanded condition, a porosity index of60-75%; windows having an inscribed diameter of 30480 microns,preferably 50-320 microns; and/or a diameter of wire filaments of 10-60microns, preferably 2040 microns; but when the filaments are ofrectangular cross-section, a circumference 40-200 microns. The foregoingparameters are significantly different from stents that have heretoforebeen used.

Experimental evidence indicates that patency can be maintained andischemia and infarction can be prevented if less than 50% of the ostialdiameter is occluded [6].

In the described preferred embodiments, the windows in the mesh-liketube produce a porosity index of preferably 60%-75%. The porosity index(P.I.) is defined by the relation:

${P.I.} = {1 - \frac{S_{m}}{S_{t}}}$

wherein: “S_(m)” is the actual surface covered by the mesh-like tube ,and “S_(t)” is the total surface area of the mesh-like tube. Theporosity index of the existing typical stents is well above 80%. In thetube devices of the present invention, however, the porosity index isnot more than 80%, preferably 55-80%, more preferably 60-75%.

In the described preferred embodiments, the mesh-like tube includeswindows having an inscribed diameter of 30-480 μm, preferably 50-320 μm,in the implanted condition of the mesh-like tube.

According to the described preferred embodiments, the mesh-like tubeincludes a plurality of filaments of bio-compatible material extendinghelically in an interlaced manner in opposite directions so as to form abraided tube. It is contemplated, however, that other mesh-likestructures could be used, such as woven or knitted tubes.

A maximum porosity index is attained when the braiding angle, in theimplanted condition of the braided tube, is 90°. Decreasing theimplanted braiding angle below 90° increases the radial force applied bythe braided tube against the inner surface of the blood vessel anddecreases the P.I. Increasing the implanted braiding angle above 90°decreases the radial force applied by the braided tube against the innersurface of the blood vessel and decreases the P.I. In cases, where lowradial force is needed, the desirable P.I. can thus be achieved byincreasing the implanted braiding angle, as described below with respectto specific examples. Preferably, the braided tube has a braiding anglein the range of 20%-150% in the implanted condition of the braided tube.

Also in the described preferred embodiments, the filaments, or at leastmost of them, are of circular cross-section and have a diameter of 10-50μm, preferably 2040 μm. The filaments could also be of non-circularcross-section, such as of square or rectangular cross-section, in whichcase it is preferred that they have a circumference of 40-200 μm. It isalso possible to use combination of several filament diameters andfilament materials in one device to achieve structural stability and/ordesired radio-opacity characteristic. Preferably the braid is formed of24-144 filaments, more preferably 62-120 filaments. The filaments may beof a suitable bio-compatible material, metal or plastic, and may includea drug or other biological coating or cladding.

According to another aspect of the present invention, there is providedan intraluminal device implantable in the vicinity of a blood vesselbifurcation, the bifurcation having a source blood vessel a first branchvessel and a second branch vessel, the aneurysm being located proximateto the bifurcation, the device comprising: a mesh-like tube ofbio-compatible material having an expanded condition in which the tubediameter is slightly larger than the diameter of the blood vessel inwhich it is to be implanted, the mesh-like tube having a lengthsufficient to be anchored to both the source blood vessel and the firstbranch vessel thereby straddling the opening of the second branchvessel; the mesh-like tube also having a contracted condition wherein itis sufficiently flexible so as to be easily manipulatable through theblood vessel so as to be placed proximate to the bifurcation; themesh-like tube being dimensioned and configured to have in its implantedcondition a porosity index of 55-80% so as to skew the flow of bloodaway from the aneurysm sufficiently to decrease the possibility ofrupture of the aneurysm but not to unduly reduce the blood flow to thesecond branch vessel to a degree likely to cause significant damage totissues supplied with blood by such second branch vessel; wherein themesh-like tube includes windows having an inscribed diameter of 30-480μm in its implanted condition.

According to yet another aspect of the present invention, there isprovided an intraluminal device implantable in the vicinity of a bloodvessel bifurcation, the bifurcation having a source blood vessel a firstbranch vessel and a second branch vessel, the aneurysm being locatedproximate to the bifurcation, the device comprising: a mesh-like tube ofbio-compatible material having an expanded condition in which the tubediameter is slightly larger than the diameter of the blood vessel inwhich it is to be implanted, said mesh-like tube having a lengthsufficient to be anchored to both the source blood vessel and the firstbranch vessel thereby straddling the opening of the second branchvessel; said mesh-like tube also having a contracted condition whereinit is sufficiently flexible so as to be easily manipulatable through theblood vessel so as to be placed proximate to the bifurcation; saidmesh-like tube being dimensioned and configured to have in its implantedcondition a porosity index of 55-80% so as to skew the flow of bloodaway from the aneurysm sufficiently to decrease the possibility ofrupture of said aneurysm but not to unduly reduce the blood flow to saidsecond branch vessel to a degree likely to cause significant damage totissues supplied with blood by such second branch vessel; wherein saidmesh-like tube is constituted of a plurality of filaments ofbio-compatible material, in which at least most of said plurality offilaments are of circular cross-section having a diameter of 10-50 μm.

According to yet another aspect of the present invention, there isprovided an intraluminal device implantable in the vicinity of a bloodvessel bifurcation, the bifurcation having a source blood vessel a firstbranch vessel and a second branch vessel, the aneurysm being locatedproximate to the bifurcation, the device comprising: a mesh-like tube ofbio-compatible material having an expanded condition in which the tubediameter is slightly larger than the diameter of the blood vessel inwhich it is to be implanted, the mesh-like tube having a lengthsufficient to be anchored to both the source blood vessel and the firstbranch vessel thereby straddling the opening of the second branchvessel; the mesh-like tube also having a contracted condition wherein itis sufficiently flexible so as to be easily manipulatable through theblood vessel so as to be placed proximate to the bifurcation; the meshlike tube being dimensioned and configured to have in its implantedcondition a porosity index of 55-80% so as to skew the flow of bloodaway from the aneurysm sufficiently to decrease the possibility ofrupture of the aneurysm but not to unduly reduce the blood flow to thesecond branch vessel to a degree likely to cause significant damage totissues supplied with blood by such second branch vessel; wherein themesh-like tube is constituted of a plurality of filaments ofbio-compatible material, in which at least most of the plurality offilaments are of rectangular cross-section having a circumference of40-200 μm.

As will be described more particularly below, intraluminal devicesconstructed in accordance with the foregoing features show great promisein the treatment of aneurysms in general, and brain aneurysms inparticular, since they are relatively easily manipulatable through theblood vessel to the implantation site, and when deployed in theirexpanded condition in the implantation site, they redirect/skew the flowof blood away from the aneurysm sufficiently to decrease the possibilityof rupture thereof while maintaining blood flow to the branch vessels inthe vicinity of the aneurysm.

Further features and advantages of the invention will be apparent fromthe description below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIGS. 1 a and 1 b are side and end view, respectively, illustrating oneform of intraluminal device constructed in accordance with the presentinvention, the device being shown in its implanted, expanded condition;

FIGS. 2 a and 2 b are corresponding views but illustrating the device inits contracted, stressed condition;

FIG. 3 more particularly illustrates the braid pattern of FIGS. 1 a, 1 band 2 a, 2 b in the expanded condition of the braided tube;

FIG. 4 illustrates another braid pattern, wherein one filament extendingin one helical direction is interwoven over and under two filamentsextending in the opposite helical direction;

FIG. 5 illustrates a further braid pattern in which two (or more)contiguous filaments extending helically in one direction are interwovenover and under two (or more) contiguous filaments extending in theopposite direction;

FIG. 6 schematically shows the relationship between the bending rigidityof the braided tube with respect to the diameter of the filamentsproducing the braided tube;

FIG. 7 schematically illustrates an intraluminal device implanted in ablood vessel having a plurality of perforating vessels in the vicinityof an aneurysm; and

FIGS. 8, 9, 10, 11 and 12 illustrate various manners in which anintraluminal device constructed in accordance with the present inventionmay be implanted in a blood vessel having an aneurysm at or proximate toa bifurcation leading to one or more branch vessels.

It is to be understood that the drawings and the description below areprovided primarily for purposes of facilitating understanding theconceptual aspects of the invention and various possible embodimentsthereof, including what is presently considered to be preferredembodiments. In the interest of clarity and brevity, no attempt is madeto provide more details than necessary to enable one skilled in the art,using routine skill and design, to understand and practice the describedinvention. It is to be further understood that the embodiments describedare for purposes of example only, and that the invention is capable ofbeing embodied in other forms and applications than described herein.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1 a and 1 b illustrate an intraluminal device, therein generallydesignated 2, constructed in accordance with the present invention inits implanted condition which it assumes in a blood vessel afterdeployment therein; whereas FIGS. 2 a and 2 b illustrate theintraluminal device 2 of FIGS. 1 a and 1 b in the contracted or stressedcondition of the device which it assumes to facilitate its manipulationthrough the blood vessel to the deployment site.

As shown particularly in FIG. 1 a, the intraluminal device includes aplurality of filaments of elastic or non-elastic bio-compatiblematerial, metal or plastic, extending helically in an interlaced mannerto define a braided tube. Thus, shown in FIGS. 1 a are a first group offilaments 3 extending helically in one direction, and a second group offilaments 4 extending helically in the opposite direction, with the twogroups of filaments being interwoven such that a filament 3 overlies afilament 4 at some points as shown at 5, and underlies a filament 4 atother points as shown at 6.

Filaments 3 and 4 thus define a braided tube having a plurality ofwindows 7. The inscribed diameter and the length of each window areshown at W_(d) and W_(L), respectively, in the implanted condition ofthe braided tube. These characteristics depend on, among other factorsincluding: the number of filaments; the cross section of the filaments;and the implanted angle “α” at the cross-over points of the two groupsof filaments 3, 4. It is understood by those skilled in the art that theabove dimensions describe the dimensions in the implanted condition ofthe braided tube. The dimensions in the fully expanded unimplantedcondition will be somewhat different, with the angle “α” and W_(L)typically being larger than, and W_(d) typically being smaller than, theequivalent respective dimensions in the implanted state.

FIG. 3 more particularly illustrates the above-described braid patternin the fully expanded condition of the braided tube. Thus, as shown inFIG. 3, each filament 3 a extending helically in one direction isinterwoven with one filament 4 a extending helically in the oppositedirection. Such a braid pattern is sometimes called a “one over one”pattern. FIG. 4 illustrates a “one over two” pattern, in which eachfilament 3 b extending helically in one direction is interwoven with twofilaments 4 b extending helically in the opposite direction. FIG. 5illustrates a further braid pattern that may be used, in which two (ormore) contiguous filaments 3 c extending helically in one direction areinterwoven with two (or more) contiguous filaments 4 c extendinghelically in the opposite direction.

The braid pattern illustrated in FIG. 3 is of highest flexibility,whereas that illustrated in FIG. 5 is of lower flexibility but of higherstrength.

Such braided-tube intraluminal devices are well-known, for example asdescribed in Wallsten et al, U.S. Pat. No. 5,061,275 and Wallsten U.S.Pat. No. 4,954,126, the contents of which are incorporated herein byreference. They are generally used as stents for providing support to awall of a blood vessel, for implanting a graft, e.g., to treat ananeurysm (FIG. 9 of the latter patent), or for other purposes. As known,the braided tube normally exhibits an expanded unimplanted conditionhaving a diameter slightly larger than the diameter of the intendedblood vessel in which it is to be implanted so that when the device isdeployed it becomes firmly embedded in the wall of blood vessel. Thebraided tube is capable of being stressed into a contracted condition,as shown in FIGS. 2 a and 2 b, wherein the diameter of the braided tubeis decreased, and its length increased, to permit manipulation of thebraided tube through the blood vessel to the site of implantation.

Further information concerning the construction and deployment of suchbraided-tube intraluminal devices is available in the above-citedpatents, and also in U.S. patent application Ser. No. 10/311,876, filedon Dec. 20, 2002, entitled “IMPLANTABLE BRAIDED STROKE PREVENTING DEVICEAND METHOD OF MANUFACTURING”, the contents of which are incorporatedherein by reference.

When such braided tubes are used as stents within blood vessels, thefilaments forming the braided tube are generally of a diameter exceeding60 μm and define windows producing a porosity index significantlyexceeding 80%. Such constructions, however, do not have the combinationof flexibility to enable them to be easily manipulated through thetortuous blood vessels of the intracranial vascular system forpreventing intracranial aneurysm ruptures, and the appropriate P.I. toenable them to skew the blood flow away form an aneurysm at or proximateto a bifurcation leading to a plurality of branch vessel.

These problems were sought to be overcome in the above-cited McCroryU.S. Pat. No. 5,951,599, Brown et al U.S. Pat. No. 6,093,199 andWallsten U.S. Pat. No. 4,954,126, in producing braided tubes having ahigh-permeability portion to be deployed in the blood vessel and alow-permeability portion aligned with the aneurysm, but as indicatedabove such braided tubes constructions are difficult to produce,difficult to manipulate through the blood vessel, and difficult toaccurately deploy at the site of the aneurysm.

According to the present invention, the constituent element making upthe mesh-like tube are of a sufficiently small size in cross-section anddefine windows of a size such that the mesh-like tube, when in itscontracted condition, is sufficiently flexible so as to be easilymanipulatable through the blood vessel to be implanted at thebifurcation; and when in its implanted condition anchoring itself toboth the source blood vessel and at least one of the branch vesselsthereby skewing flow of blood away from the aneurysm sufficiently todecrease the possibility of rupture of the aneurysm. The skewing iscaused by the flow of blood through the walls of the mesh-like tube, andthe amount of skew is a function of the predetermined implanted porosityindex. In an exemplary embodiment, in which the mesh-like tube isconstituted of braided filaments, the windows defined by the filamentsof the braided tube are such as to reduce the flow of blood therethroughto the aneurysm to decrease the possibility of rupturing it, but not tounduly reduce the blood flow to the branch vessels to the degree likelyto cause damage to tissues supplied with blood by such vessels. Asindicated earlier, experimental evidence indicates that patency can bemaintained, and ischemia and infarction can be prevented, if less than50% of the ostial diameter of the branch vessel is occluded. The ostialdiameter of intercranial branch vessels are typically on the order of80-800 μm, thus to ensure patency of the intercranial branch vessels,filaments of the braided tube must be less than 50 μm in diameter forround filaments, and preferably less than or equal to 40 μm. Fornon-round filaments, a similar dimensional limitation is necessary.

FIG. 6 schematically illustrates how the bending rigidity or flexibilityof a braided tube varies with the diameter of the filaments. Region A inFIG. 6 illustrates typical diameters in conventional stents used forsupporting blood vessels, which region usually starts above 60 μm andextends to several hundred μm. Region B in FIG. 6 illustrates the regionof filament diameters for use in constructing braided tubes inaccordance with the present invention. The filament diameters in thisregion would be significantly smaller than in region A, preferably being10-50 μm, more preferably 20-40 μm.

The foregoing dimensions apply to the diameters of filaments of circularcross-section. Where the filaments are of non-circular cross-section,such as of rectangular or square cross-section, the filaments wouldpreferably have a circumference of 40-200 μm. The circumference isdefined in macro scale. The circumference can be enlarged at themicro-scale level by adding roughness to the wire, in order to controlthe neointimal growth and making the circumference in micro scale longerwhile keeping the macro scale the same. In this case the surface crosssection of the filament would be in the range 75-3000 μm^(̂2) preferably300-1300 μm^(̂2).

As indicated earlier, the windows formed in the braided tube would alsobe preferably within a predetermined range such as to skew theblood-flow away from the aneurysm, but maintain sufficient blood flow inthe or branch vessels. Preferably the length of the window, i.e., itslong dimension as shown at W_(L) in FIG. 1 a, would be within the rangeof 30-480 μm, more preferably 50-320 μm, in the implanted condition ofthe braided tube. Also, the implanted angle (α, FIG. 1 a) wouldpreferably be within the range of 20°-150°, more preferably 40-80° forhigh radial force and 100-140° for low radial force, in the implantedcondition of the braided tube. In yet another preferred embodiment thebraid angle in the implanted condition is approximately 90°, preferablyin the range of 70°-110°.

The diameter and length of the braided tube in its normal, implantedcondition, will vary according to the location and anatomical dimensionsat the particular site of the implantation. Preferably, the windows arepreferably globally (but not necessary locally) uniform in size suchthat any portion of the device can be placed across the opening of thebranch vessel to skew the blood flow away from the aneurysm locatedproximate thereto, while the remaining portions of the device firmlycontact the walls of the source blood vessel and at least one branchvessel thereby securely anchoring the device.

The filaments of the exemplary braided embodiment can be made of anysuitable material which are bio-compatible and which can be worked intoa braid. Bio-compatible herein includes any material that can be safelyintroduced and implanted in human or animal bodies for indefiniteperiods of time without causing any significant physiological damage.Preferably, the filaments are made of a material selected from among the316L stainless steel, tantalum, and super elastic Nitinol, cobalt basealloy, polymer or any other suitable metal or metal combination. Thefilament can be coated with bio-compatible coatings [Ulrich Sigwart,“Endoluminal Stenting”, W. B. Saunders Company Ltd., London, 1996]. Itis possible to use a combination of several filament materials in onedevice and combinations of several materials in one filament. The aboveembodiments have been described in relation to a braid mesh tube,however this is not meant to be limiting in any way. Other mesh-likestructures, such as woven or knitted tubes exhibiting similar porosityand flexibility can be used without exceeding the scope of theinvention.

In some situations, it may be desired to implant the device in a portionof a lumen, e.g., an artery, varying significantly in diameter along itslength. As will be appreciated, if a constant diameter braided tubedevice is inserted into such a variable-diameter lumen, this may resultin a defective anchoring of the device at the larger diameter portion ofthe lumen, and in a possible risk of the migration of the device withinthe lumen. This problem can be easily overcome in several ways, e.g., bycreating braided devices with variable diameters along theirlongitudinal axis, or varying the pitch along the longitudinal axis, asdescribed in the above-cited U.S. patent application Ser. No. 10/311,876incorporated herein by reference.

FIG. 7 diagrammatically illustrates the mesh-like tube device, thereingenerally designated 20, implanted in a blood vessel 22 having side wallaneurysm 29 in a region of a blood vessel 22 having a plurality ofperforating vessels 26. Mesh-like tube device 20 is introduced, in itscontracted condition, into blood vessel 22 and is manipulated to theimplantation site by a microcatheter 28 where it is expanded such thatit overlies neck 30 of aneurysm sac 29 and perforating vessels 26.Mesh-like tube 20 is thus firmly bonded, by its expansion to animplanted state, to the inner surfaces of blood vessel 22. As describedabove, braided tube device 20 is constructed such that, in its expandedimplanted condition as shown in FIG. 4, it reduces the flow of blood toside wall aneurysm sac 29 sufficiently to decrease the possibility ofrupture thereof, while at the same time, it does not unduly reduce theflow of blood to perforating vessels 26 to the degree likely to causedamage to the tissue supplied by perforating vessels 26. In a preferredembodiment the porosity index of braided tube device 20 overlying neck30 of aneurysm sac 29 is between 55-80%, preferably 60-75%.

FIGS. 8, 9 and 10 illustrate the use of the braided tube device,generally designated 30, to treat an aneurysm in a blood vessel at orproximate to a bifurcation leading to two or more branch vessels.

Thus, FIG. 8 illustrates the braided tube device 30 implanted in a bloodvessel 32 having an aneurysm 34 at the bifurcation leading to two branchvessels 36, 38. In the example illustrated in FIG. 8, the braided tubedevice 30 is deployed with one end embedded in the blood vessel 32 andthe opposite end embedded within first branch vessel 36, so as to skewthe blood flow away from the aneurysm sac 34, illustrated by flow lines40 without unduly impeding blood flow to second branch vessel 38. Asdescribed earlier, however, while the reduced blood flow to the aneurysmsac 34 is sufficient to reduce the possibility of rupture of the sac,the reduced blood flow to second branch 38 is not sufficient so as to belikely to cause damage to the tissues supplied by that branch vessel. Inan important aspect of the arrangement of FIG. 8, braided tube device 30does not directly overly aneurysm sac 34. Flow lines 40 illustrate theblood flow exiting braided tube device 30 substantially bypassinganeurysm sac 34. Reducing the porosity index of braided tube device 30increases the skew of blood flow from its normal path against inner wall42 of second branch vessel 38, and redirects the flow towards outer wall44 of second branch vessel 38. Further skewing of blood flow towardsouter wall 44, thus bypassing aneurysm sac 34, is accomplished byincreasing the pore density, defined as the number of pores per unitarea. An increase in pore density is accomplished for the same porosityindex by reducing the filament size, thus increasing the contact betweenblood particles and filaments. In a preferred embodiment, the porosityindex is between 55-80%, preferably 60-75%.

FIG. 9 illustrates a variation wherein the opposite ends of the braidedtube 30 are embedded in two branch vessels 36 and 38 at the bifurcation.In this case, the blood supply to the aneurysm sac 34 will also bereduced, and blood supply to both branch vessels 36, 38 will be reducedbut not sufficient to cause damage to the tissues supplied by thosebranch vessels.

FIG. 10 illustrates an embodiment in which aneurysm sac 34 occupies thebasal apex of bifurcation of blood vessel 32 into first branch vessel 36and second branch vessel 38. Normal stenting of such a basal apexaneurysm sac is quite difficult, since the only approach to such ananeurysm in many cases is from blood vessel 32 or through the anteriorvessels via the communication posterior arteries. This is particularlydifficult in an intracranial embodiment, for which access must beaccomplished through torturous blood vessels. Mesh-like tube device 30is inserted through blood vessel 32 into first branch vessel 36, andexpanded to its implanted state thus being securely embedded against thewalls blood vessel 32 and first branch vessel 36. In a preferredembodiment mesh-like tube device 30 is of the self-expanding type. In anexemplary embodiment, mesh-like tube device 30 is a braidedself-expanding type. In an important aspect of the arrangement of FIG.10, mesh-like tube device 30 does not directly overly aneurysm sac 34,

In operation blood flow from source blood vessel 32 to branch vessel 36is unimpeded. Blood flow from source blood vessel 32 to branch vessel 38is reduced due to a P.I. of less than 100%, however not sufficient tocause damage to the tissues supplied by branch vessel 38. The P.I. isselected to skew the blood flow away from aneurysm sack 34 towardsbranch vessel 38 as shown by flow lines 40. The blood flow whichnormally would directly impact aneurysm sack 34 is redirected away fromaneurysm sack 34 and vessel wall 44 of branch vessel 38, to flow towardsvessel wall 42 of branch vessel 38.

FIG. 11 shows another embodiment in which aneurysm sac 34 occupies thebasal apex of bifurcation of source blood vessel 32 into first branchvessel 36 and second branch vessel 38. Two mesh-like tube devices 30 areinserted through blood vessel 32 into branch vessels 36 and 38,respectively and are expanded to their implanted state thus beingsecurely embedded against the walls of source blood vessel 32, andbranch vessels 36 and 38, respectively. In a preferred embodiment bothmesh-like tube devices 30 are of the self expanding type. In anexemplary embodiment, mesh-like tube devices 30 are a braidedself-expanding type. The P.I. is selected to skew the blood flow awayfrom aneurysm sack 34. In an important aspect of the arrangement of FIG.11, mesh-like tube devices 30 do not directly overly aneurysm sac 34.

FIG. 12 shows another embodiment in which aneurysm sac 34 occupies thebasal apex of bifurcation of blood vessel 32 into first branch vessel 36and second branch vessel 38. A mesh-like tube device 30 is insertedthrough source blood vessel 32 into branch vessel 36 and expanded to itsimplanted state thereby being securely embedded against source bloodvessel 32 and branch vessel 36. A mesh-like tube device 50 is insertedthrough mesh-like tube device 30 into branch vessel 38 and is expandedto its implanted state thus being securely embedded against the walls ofsource blood vessel 32 and branch vessel 38. In a preferred embodimentmesh-like tube devices 30 and 50 are of the self-expanding type. In anexemplary embodiment, mesh-like tube devices 30 and 50 are a braidedself-expanding type.

Blood flow from source blood vessel 32 to first branch vessel 36 isunimpeded, and blood flow from source blood vessel 32 to second branchvessel 38 is unimpeded. Blood flow to aneurysm sac 34 is reduced by theskewing effect of mesh-like tube devices 30 and 50. In an importantaspect of the arrangement of FIG. 12, mesh-like tube devices 30 and 50do not directly overly aneurysm sac 34.

Analysis of a model similar to the setup illustrated in FIG. 8 wasaccomplished, in which the angle between the axis of branch blood vessel38 and the axis of blood vessel 32 was approximately 30°, and the anglebetween the axis of branch blood vessel 38 and the wall of braided tubedevice 30 was approximately 55°. In the absence of braided tube device30, representative of a PI of 100%, blood flow directly impacted thelocation of aneurysm 34 with a near 0° angle. Utilizing a braided tubedevice 30 exhibiting a PI of 85% skewed the blood flow near aneurysm 34approximately 40° from the axis of blood vessel 32. Reducing the PI ofbraided tube device 30 to 74% increased the skew of the blood flow nearaneurysm 34 to approximately 55° from the axis of blood vessel 32. Thus,a reduced PI successfully skewed the blood flow from directly impactinganeurysm 34.

While the invention has been described with respect to several preferredembodiments, it will be appreciated that these are set forth merely forpurposes of example, and that many other variations, modifications andapplications of the invention may be made. For example, the device couldbe composed of multiple tubular meshes, lying one above the other inlayer-like formations. Also, the device could include a plurality ofgroups of filaments in the longitudinal and/or circumferentialdirection. Further, the invention could be implemented with respect tomany of the other variations and applications described in theabove-cited International Application PCT/IL01/00624, equivalent to U.S.patent application Ser. No. 10/311,876, published as U.S. PatentApplication Publication No. 2004/0024416 incorporated herein byreference.

REFERENCES

-   1. An International Study of Unruptured Intracranial Aneurysms    Investigators. N Engl J Med. 1998 December 10;339(24):1725-33:    International study of unruptured intracranial aneurysms    investigators; Unruptured intracranial aneurysms-risk of rupture and    risks of surgical intervention.-   2. Bederson J B, Awad I A, Wiebers D O, Piepgras D, Haley E C Jr,    Brott T, Hademenos G, Chyatte D, Rosenwasser R, Caroselli C.;    Recommendations for the management of patients with unruptured    intracranial aneurysms: A Statement for healthcare professionals    from the Stroke Council of the American Heart Association. Stroke.    2000 November;31(11): 2742-50. No abstract available.-   3. Wardlaw J M, White P M. The detection and management of    unruptured intracranial aneurysms. Brain. 2000 February;123 (Pt    2):205-21. Review.-   4. Wakhloo A K, Lanzino G, Lieber B B, Hopkins L N. Stents for    intracranial aneurysms: the beginning of a new endovascular era?    Neurosurgery. 1998 August;43(2):377-9.-   5. Lieber B B, Stancampiano A P, Wakhloo A K. Alteration of    hemodynamics in aneurysm models by stenting: influence of stent    porosity. Ann Biomed Eng. 1997 May-June;25(3):460-9.-   6. Lanzino G, Wakhloo A K, Fessler R D, Hartney M L, Guterman L R,    Hopkins L N. Efficacy and current limitations of intravascular    stents for intracranial internal carotid, vertebral, and basilar    artery aneurysms. J Neurosurg. 1999 October;91(4):53846.-   7. Yu S C, Zhao J B. A steady flow analysis on the stented and    non-stented sidewall aneurysm models. Med Eng Phys. 1999    April;21(3):133-41.-   8. Marinkovic S, Gibo H, Milisavljevic M, Cetkovic M. Anatomic and    clinical correlations of the lenticulostriate arteries. Clin Anat.    2001 May;14(3): 190-5.

1. An intraluminal device implantable in a blood vessel having ananeurysm, comprising: a braided mesh-like tube of bio-compatiblematerial having an expanded condition in which the tube diameter islarger than the diameter of the blood vessel in which it is to beimplanted, and having a length sufficient to be anchored at both ends tosaid blood vessel and to straddle said aneurysm; said braided mesh-liketube being constituted of 24-144 filaments, and being designed to havein its implanted condition a porosity index of 60-75% and windows havingan inscribed diameter of 50-320 μm, so as to skew the flow of blood awayfrom the aneurysm sufficiently to decrease the possibility of rupture ofsaid aneurysm.
 2. The intraluminal device according to claim 1, whereineach of said filaments has a circular cross-section having a diameter of10-50 μm.
 3. The intraluminal device according to claim 1, wherein saidbraided mesh-like tube is formed of 62-120 filaments of bio-compatiblematerial.
 4. The intraluminal device according to claim 1, wherein saidbraided mesh like tube is constituted of a single tubular mesh.
 5. Theintraluminal device according to claim 1, wherein said braided mesh-liketube is constituted of multiple tubular meshes, lying one above theother in layer-like formations, in the implanted condition of thebraided mesh-like tube.
 6. A method of treating an aneurysm in a bloodvessel, comprising: implanting in the blood vessel a braided mesh-liketube of bio-compatible material having an expanded condition in whichthe tube diameter is larger than the diameter of the blood vessel inwhich it is to be implanted, and having a length sufficient to beanchored at both ends to said blood vessel and to straddle saidaneurysm; said braided mesh-like tube being constituted of 24-144filaments, and being designed to have in its implanted condition aporosity index of 60-75% and windows having an inscribed diameter of50-320 μm, so as to skew the flow of blood away from the aneurysmsufficiently to decrease the possibility of rupture of said aneurysm. 7.The method according to claim 6, wherein each of said filaments has acircular cross-section has a diameter of 10-50 μm.
 8. The methodaccording to claim 6, wherein said braided mesh-like tube is formed of62-120 filaments of bio-compatible material.
 9. The method according toclaim 6, wherein said braided mesh-like tube is constituted of a singletubular mesh.
 10. The method according to claim 6, wherein said braidedmesh-like tube is constituted of multiple tubular meshes, lying oneabove the other in layer-like formations, in the implanted condition ofthe braided mesh-like tube.
 11. An assembly for implanting anintraluminal device in a selected site of a blood vessel having ananeurysm, the assembly comprising: an intraluminal device, whichcomprises a braided mesh-like tube of bio-compatible material having anexpanded condition in which the tube diameter is larger than thediameter of the blood vessel in which it is to be implanted, and havinga length sufficient to be anchored at both ends to said blood vessel andto straddle said aneurysm; said braided mesh-like tube being constitutedof 24-144 filaments, and being designed to have in its implantedcondition a porosity index of 60-75% and windows having an inscribeddiameter of 50-320 μm, so as to skew the flow of blood away from theaneurysm sufficiently to decrease the possibility of rupture of saidaneurysm; and a microcatheter for delivering said intraluminal device tosaid selected site in the blood vessel and for implanting it therein.12. The assembly according to claim 11, wherein each of said filamentshas a circular cross-section having a diameter of 10-50 μm.
 13. Theassembly according to claim 11, wherein said braided mesh-like tube isformed of 62-120 filaments of bio-compatible material.
 14. The assemblyaccording to claim 11, wherein said braided mesh-like tube isconstituted of a single tubular mesh.
 15. The assembly according toclaim 11, wherein said braided mesh-like tube is constituted of multipletubular meshes, lying one above the other in layer-like formations, inthe implanted condition of the braided mesh-like tube.